Good morning!! Can someone help, please An experienced bricklayer can work twice

Question

Good morning!! Can someone help, please

An experienced bricklayer can work twice as fast as an apprentice bricklayer. After they work together on a job for 6 hours, the experienced bricklayer quits. The apprentice requires 10 more hours to finish the job. How long would it take the experienced bricklayer, working alone, to do the job? 4 A roofer requires 8 hours to shingle a roof. After the roofer and an apprentice work on a roof for 2 hours, the roofer moves on to another job. The apprentice réquires 10 more hours to finish the Job. How long would it take the apprentice, working alone, to do 5. the job?

Explanation / Answer

4. Since the experienced bricklayer works twice as fast as the apprenticed bricklayer, we can say when they work together, there are three apprenticed bricklayers working.

Number of person-hours taken by the "three" bricklayers = 3 * 6 = 18.

Number of person hours taken by the lone bricklayer to finish the rest of the job = 1 * 10 = 10.

=> Total person-hours to finish the job = 18 + 10 = 28.

Thus it would take 28 hours for the apprentice to finish the job alone.

5. The roofer takes 8 hours to finish the job alone.

In the 2 hours the roofer works together with the apprentice, the roofer finishes 2/8 = 1/4th of the job.

=> 3/4th of the job remains.

The apprentice takes 2 hours + 10 hours = 12 hours to finish 3/4 th of the job

=> Time taken by the apprentice if working alone = 12 / (3/4) = 16 hours.

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